Mock test failing for boto3.client(ec2-instance-cpnnect).send_ssh_public_key

Question

I have the following code for ssh using instance id.

filename.py - 
def command(self,args):
    ec2connect = boto3.client('ec2-instance-connect')
    ec2connect.send_ssh_public_key(
        InstanceId=args.instance_id,
        InstanceOSUser=user_name,
        SSHPublicKey=ssh_key_string,
        AvailabilityZone=instance['Placement']['AvailabilityZone'])
    out("connecting")
    os.execl("user/bin/ssh","ssh","-l", username, ip_address)

def out(message):
    print(message)

I am trying to test it by mocking my command function, I have tried @mock.patch(filename.command.botocore.session.Session.create_client)

and then asserting the message "connecting" to see if this ssh functionality is working. However I keep getting assertion failed. I am wondering if my mock patch is wrong and if there is a better way to mock ec2instanceconnect.